slot type not equal plugs type

[Alekseenko Vasilii]

For example

# snap install nmap
6.25 MB / 6.27 MB 
[======================================================================================================================================================================>_] 
99.68 % 1.02 MB/s

# snap interfaces
Slot                 Plug
:firewall-control    -
:home                -
:locale-control      -
:log-observe         -
:mount-observe       -
:network             nmap
:network-bind        nmap
:network-control     -
:network-observe     -
:opengl              -
:snapd-control       -
:system-observe      -
:timeserver-control  -
:timezone-control    -
:unity7              -
:x11                 -
-                    nmap:network-control